The core team at UAF continues to support PISM users. The new email for help is firstname.lastname@example.org; it replaces email@example.com. As before, email to this address will be distributed to all the UAF developers, and so it will get the most prompt response year-round.
The 4000 square km ice field in Southeast Alaska is well-known and accessible since its outlets are in the suburbs of the Alaska state capital, Juneau. But climate data for the area are sparse.
Those model runs that agreed well with observations for 1971 to 2010 generated volume and area losses of more than half by 2099. While co-author Regine Hock (UAF) is quoted as saying “The massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true,”, the authors emphasize that spatially-distributed mass balance measurements and improved climate projections that resolve the local temperature and precipitation patterns are essential to solidifying these predictions.
Please acknowledge the funding that makes PISM possible, and which supports its continued maintenance and technical support. Include the sentence “Development of PISM is supported by NASA grants NNX13AM16G and NNX13AK27G.” in the Acknowledgments part of your paper.
If authors do this consistently then it will help to ensure continued funding of PISM!
For specific suggestions on how to cite the design or justification of PISM see this page.
The Paleoclimate Dynamics section at Alfred-Wegener-Institut invites applications for a position as a
with a background in ice sheet or climate modelling for the DFG-project “Global sea level change since the Mid Holocene” (SPP 1889).
Background and tasks:
The aim of this project is to study the evolution of polar ice sheets of the last 6000 years and to estimate the role of climate – ice sheet interactions. Combining climate and ice sheet simulations of different resolution, the project particularly focusses on the ice sheets' mass balance and on ice shelf – ocean interactions under natural and anthropogenic climate change.
The postdoc’s duties will include set-up, supervision, and analysis of climate and ice sheet (PISM) simulations as well as publication in peer-reviewed journals.
The successful candidate should have a PhD in glaciology, atmospheric sciences, oceanography or related sciences and should have a background in either ice sheet or climate modelling.
The position is limited to 3 years, starting August 1st, 2016 or later. The salary will be paid in accordance with the German Tarifvertrag des öffentlichen Dienstes (TVöD Bund), salary level 13. The place of employment will be Bremerhaven.
For further information:
PETSc 3.7 was released on April 25, 2016. We are currently working on making PISM compatible with PETSc 3.7 and will announce it here as soon as possible.
In the meantime, please install petsc 3.6.4 from here. PISM version 0.7 (
stable0.7 branch) works with any PETSc 3.5.X and higher.
The paper is based on PISM simulations with grid resolution down to 600 m over the entire Greenland ice sheet. To start, each of an initial ensemble of 14 lower-resolution (1500 m) experiments has a single ice-sheet-wide value for all parameters. The best of these, in an ice-sheet-wide measure, is re-run at the 600 m resolution and various coarser resolutions. The quality of this flow model for 29 outlet glaciers is assessed; each outlet glacier sees the same physics. The main result is that the majority of the outlet glaciers show strong correlation between modeled and present-day-observed velocity, when it is compared along cross-flow and near-ocean profiles.
Before this paper one might suppose, based on the most prominent literature on the subject, that a detailed, measurably-accurate, outlet-glacier-resolving model of the present-day velocity of an entire ice sheet was dependent both on removing shallow assumptions from the stress balance and on tuning a very large number of basal parameters. Both of these “required” properties would be very bad news for the prospect of using ice sheet simulations to do science! On the one hand, Stokes models are computationally-expensive, while on the other hand only present-day, and not past or future, data are available to set all these basal parameters through inversion.
Such a pessimistic view turns out to be substantially false. Aschwanden et al. (2016) show that four things do matter: (i) an accurate map of bedrock topography, (ii) a stress regime in which viscous membrane stresses are part of the balance with basal sliding resistance, (iii) an energy-conservation-driven basal stress model derived (conceptually) from a model of a wet, pressurized, deformable basal layer, and (iv) high model resolution over all areas of the ice sheet where sliding is possible and/or steep/rough basal topography exists.
NASA IceBridge missions, and the mass-conserving-bed technology of Morlighem et al (2014), are shown by this paper to represent major progress on item (i). Items (ii) and (iii) are properties of the PISM continuum model, and item (iv) of its implementation as parallel-scalable software. Certainly all of these “things that matter” are improvable. More-complete stress balances and the use of inversion of present-day velocities will both be essential to improvements. The main idea remains, however: if the modeled flowing ice has the right bottom geometry, and if the dynamical model has certain key features, then the resulting dynamics are already inside the ballpark!
See the official announcement for complete details.
The Antarctic Research Centre, Victoria University of Wellington, New Zealand, is offering a FULLY FUNDED scholarship for an enthusiastic and talented Ph.D student to undertake numerical ice-sheet modelling research. Experiments will focus on better understanding and simulating the processes involved in ice-sheet – ocean interactions. Such processes determine the basal mass balance of marine-based ice-sheets such as the West Antarctic Ice Sheet, and as such, control the pattern and timing of grounding-line migrations.
Collaborating with scientists at a variety of New Zealand (VUW, GNS, NIWA) and Australian (UNSW, UTAS, AAD) institutions, the researcher will use present-day glaciological and oceanographic observations as primary constraints to a suite of model simulations that will explore the sensitivity of Antarctic ice-sheets to changes in ocean circulation. A key aspect of the project lies in trying to identify and quantify thresholds and feedback mechanisms that may either accelerate or inhibit ice-shelf melt. The ultimate aim of the project is to build on recent work to provide more robust simulations of ice-shelf and ice-sheet changes under future scenarios of perturbed atmospheric and oceanographic conditions.
The research project will span a range of temporal and spatial scales, but will primarily use the Parallel Ice Sheet Model and will focus initially on the Ross Ice Shelf. The successful applicant may also have the opportunity to spend time in Antarctica acquiring new data.
Skills: Applicants must have a strong background in geophysics, maths or other numerical Earth Sciences. Experience working in a UNIX / Linux environment, including shell scripting, is essential. Programming abilities in any of the usual languages and experience with high-performance computing facilities would also be extremely useful.
Applications: We wish to have the successful applicant starting no later than July 2016, and therefore request completed applications by 18th December 2015.
For details of the application process or to lodge an expression of interest, contact Dr. Nick Golledge (firstname.lastname@example.org) as soon as possible.
A new paper in the Proceedings of the National Academy of Sciences by J. Feldmann and A. Levermann, of the Potsdam Institute for Climate Impact Research, uses PISM simulations to show that nearly-complete WAIS collapse is triggered by present-day melt rates in the Amundsen Sea. Modeled WAIS deglaciation follows after relatively-short (60–200a) periods in which the present-day sub-shelf (i.e. ocean-caused) melt rates are sustained.
The simulations use conservative assumptions about, and (necessarily) modeling of, the interaction of the ice sheet with the ocean and atmosphere. In particular, subshelf melt rates for the present ice shelf geometry are taken from Finite Element Sea Ice-Ocean Model (FESOM) results. These are then extended to the evolving cavity geometry by a diffusive algorithm into regions below sea level, but with a pressure adjustment using the ice shelf base elevation. This leads to melt rates further inland that are similar to corresponding present-day-cavity-geometry-induced melt rates.
In most other ways this application of PISM is as expected, though at high (5km) resolution and using a full suite of marine ice sheet submodels: 50ka spinup, SIA+SSA model with plastic till, subgrid motion of the calving front, ocean-water stress boundary condition at the calving front, the "eigen-calving" calving law, and an interpolated grounding line.
The results of the simulations are most easily understood by seeing what happens:
This work appeared today, 2 November 2015. It is already featured in commentaries at the Washington Post, The Guardian, and Bloomberg Business News. It is also featured in Nature journal's "News:Explainer", and in Science magazine's "Latest News".
The last of these includes this high-level view from two well-known students of the behavior of Amundsen Sea-sector glaciers:
“This paper does confirm what we hypothesized, that knocking out the Pine Island Glacier and Thwaites takes down the rest of the West Antarctic Ice Sheet,” says Ian Joughin, a glaciologist at the University of Washington, Seattle, who co-authored last year’s Science paper. He adds, however, that the model’s weakness is its [temporal] resolution; it shows the destabilization of the glaciers occurring roughly 60 years from now, whereas present observations suggest that collapse is already underway. As a result, Joughin says, the model’s time scale for the collapse is probably too long. “It’s more likely measured in centuries rather than millennia.”
Indeed, “the jury is still out” on whether Feldmann and Levermann’s study got the time scale right, [Eric] Rignot [of the University of California, Irvine] says. The long-term evolution of an ice sheet “is a very complex modeling problem. Some of the variables controlling the models are not all that well known,” he adds, including forces such as winds, ocean circulation, and how icebergs calve. “There is not a model out there that is getting it right, because they all have caveats. I think the discussion is ongoing, and is only going to be more interesting with time.”
As a result of the buzz around Winkelmann et al. (2015)'s modeling of the effect of full conversion of available fossil fuels in the ground into atmospheric CO2, using PISM for determining ice dynamics/response timescale, on 5 October our local paper the Fairbanks Daily News Miner featured PISM. The content is a bit warped by scientist-to-journalist transmission issues, but we are happy to have local recognition of this UAF-lead project!
See the official position announcement here.
We are looking for a candidate who is interested in taking part in the research project “Modelling the ice flow in the western Alps during the last glacial cycle” which is a joint initiative between ETH Zurich and the University of Bern (Prof. Christoph Raible and Dr. Juan Jose Gomez-Navarro). The objective is to better understand the chronology of the last glaciation over the Alps via a modelling approach. The core of this doctoral research will be to model the ice flow and the glacial extent in the western Alps during the last glacial cycle. For that purpose, the PhD student will set up and run the Parallel Ice Sheet Model (PISM) on the clusters of the Swiss National Supercomputing Centre. The crucial step in setting up in PISM will be to include high-resolution climate simulation results, which will be conducted at the University of Bern. The combination of the two state-of-the-art models (ice flow and climate) will give a new insight of the ice flow field prevailing in the western Alpine region during some periods of interest like the last glacial maximum (22000 BP) and an earlier period (65000 BP). The final goal of the PhD will be to compare the new model results to the geomorphological evidence left on the Swiss landscape during the last glacial cycle (e.g. moraines, erratic boulders) in collaboration with quaternary geologists of EHT Zurich. The PhD student will be supervised by Dr. Guillaume Jouvet and Prof. Martin Funk.
The ideal candidate has a master degree either in geophysics, earth sciences, physics, applied mathematics, computer science, or a related field, and a keen interest in modelling of geophysical processes. Previous experience in computer modelling and scientific programming languages (C/C++, Python, Matlab) is an asset. Good writing and communication skills as well as the motivation to fruitfully collaborate within an interdisciplinary framework are essential, in particular with our climate modelling partners at the University of Bern.
For additional information please refer to www.glaciology.ethz.ch or contact Dr. Guillaume Jouvet, email@example.com (no applications).
A new open-access paper by Ricarda Winkelmann and others uses PISM to address an admittedly extreme question: If all currently-attainable fossil fuel resources are converted to atmospheric greenhouse gases, what happens to the Antarctic Ice Sheet?
This paper's model-based answer is that serious destruction of the ice sheet occurs in the first millenium, at about 3 m sea level rise per century. Such a large mass loss rate tails off in the two following millenia. The large losses come from a combination of marine-ice-sheet instability and surface elevation versus mass balance feedback, both of which are modeled effects in PISM. However, in the first century of the simulations there are the same relatively-modest AIS mass changes as seen in other recent modeling work, because dynamic losses driven by increasing ocean temperatures are partly offset by increasing snowfall.
Here is a quick methods summary, with more detail found in the paper and its supplementary material: Emission scenarios, CO2 concentrations, and global mean temperature pathways are combined in an Earth system model and then downscaled to surface and ocean temperature anomalies for Antarctica. These regional warming scenarios are then used to force PISM, in particular using its positive-degree-day scheme to model surface melt and a three-equation model for subshelf melting.
US National Public Radio featured the paper, including comments by co-author Ken Caldeira, on the 11 September edition of All Things Considered, as did the New York Times.
This is a re-posting of the CRYOLIST announcement from Uwe Mikolajewicz
The Max Planck Institute for Meteorology (MPI-M) is a multidisciplinary center for climate and Earth system research located in Hamburg, Germany. MPI-M contributes to the BMBF project “From the Last Interglacial to the Anthropocene: Modeling a Complete Glacial Cycle” (PalMod), which aims at simulating the climate from the peak of the last interglacial up to the present using comprehensive Earth System Models.
With respect to this research project, we have an open position for a
The successful candidate will be part of a local team performing and analyzing transient simulations from the last Glacial to the Holocene with an interactively coupled atmosphere-ocean-ice sheet model. Additionally the candidate will contribute to the development of this model. The model system will consist of the MPI-Earth system model and the ice sheet model PISM.
For information on PhD Fellowships in Earth System Modeling at MPI-M, see
PISM v0.7.1 was released 30 June 2015. In addition to bug fixes this version adds support for PETSc 3.6.1, which was released 22 July 2015.
PETSc 3.6.0 is not supported due to a bug in PETSc. Please use PETSc 3.5.4 or >= 3.6.1 with PISM.
It's summer time! UAF PISM developers are currently writing proposals, working on their own projects, and enjoying the summer. Please give us some slack responding to questions, bug reports, etc. We will try to fix serious bugs as quickly as possible . We'll be back at full strength in the Fall.
PETSc 3.6 was released on June 9, 2016. We are currently working on making PISM compatible with PETSc 3.6 and will announce it here as soon as possible.
In the meantime, please install petsc 3.5.4 from here. PISM version 0.7 (
stable0.7 branch) works with any PETSc 3.5.X.
This release has substantial changes to the code base, but users will not see large differences. The goal of most code changes is to improve maintainability, and our speed in fixing bugs and adding features, so we ask users to update from v0.6 unless they have a good reason against it.
If you already have a git repo for pism then upgrade by doing
git fetch origin git checkout stable0.7
in the PISM source tree. (Or get a new tagged
.zip at github.com/pism/pism/releases.) Then do
in the build directory.
The install directions in
INSTALL.md, included in the source release, should help with installation errors, but there is also an Installation Manual. Feel free to email firstname.lastname@example.org with installation questions; please include the failed commands and the error message(s).
Lists below give user-visible changes. For a full list of changes since v0.6, please see CHANGES.md in the source release.
Please send email to email@example.com for help with any version of PISM.
At the AGU Fall Meeting 2014, PISM simulations and results were featured in a number of posters and oral presentations.
In a new Nature Communications paper, researchers at Victoria University and the University of New South Wales describe a model study of Antarctic ice sheet evolution over the last 25 kyr using PISM with ocean-forcing inputs from the Earth system model LOVECLIM. They show that when the ocean around Antarctica becomes more stratified, warm water at depth melts the ice sheet faster than when the ocean is less stratified.
The study used a large ensemble of 15 km PISM simulations in a data-constrained mode. In the simulations that best fit a variety of temporal and spatial observations, several episodes of accelerated ice-sheet recession occurred, with the timing of the largest being coincident with meltwater pulse 1A. This episode saw an abrupt rise in global sea level, with an Antarctic contribution of nearly three meters over just a few centuries.
In a Geoscientific Model Development Discussion paper, UAF author Ed Bueler and IMAU author Ward Van Pelt describe PISM's new mass conserving subglacial hydrology models.
For the PISM user with an interest in subglacial hydrology this paper provides a detailed description of all the subglacial hydrology models available in PISM versions v0.6 and above, along with a stability analysis, verification, and an application to the Greenland ice sheet.
Only fixes and improvements that should not break existing functionality are included in this release. We recommend updating from v0.6 unless you have a good reason against it. Upgrade by doing “git pull” in the PISM source tree. (Or get a new tagged “.tar.gz” or “.zip” at github.com/pism/pism/releases.) Then do “make install” in the build directory.
For a full list of changes since v0.6, please see https://github.com/pism/pism/blob/stable0.6/CHANGES.md
Send email to firstname.lastname@example.org for help with any version of PISM.
In a just-published Nature Climate Change article, Potsdam Institute for Climate Impact Research authors Matthias Mengel and Anders Levermann use PISM to define the “ice-plug” which, if removed from the coastal ice in the Wilkes Basin of East Antarctica, would initiate irreversible retreat of the grounded ice in that basin. The modeled retreats, which occur on a time scale of a few thousand years, generate 3–4 m of sea level rise from the region surrounding the basin. Thus this basin is a potential “tipping-point” ice sheet configuration, in additional to the better-known West Antarctica configurations.
For the PISM user this paper is an indication of its ability to model an ice sheet region (hashed in figure) at high resolution across a range of ice dynamics parameters and climate forcing choices.
This Science Daily news item quotes the authors about this work.
See the stable version page to check out a copy of the PISM stable0.6 source code. If you have already checked out the prerelease version, just do
git pull and then
make install in your build directory. Send email to email@example.com for help with any version of PISM.
Changes since stable0.5 include
Please see the PISM's Python Documentation.
Since 2012 there have been seven Ph.D. students who have completed their degrees using PISM as a major tool in their research. The new year is a good time to feature their accomplishments on the PISM front page!
A dynamic memory of fracture processes in ice shelves, Ph.D. Potsdam University 2013; advisor A. Levermann; publications including Albrecht et al. (2011) and Albrecht and Levermann (2012); personal webpage
Basal shear strength inversions for ice sheets with an application to Jakobshavn Isbrae, Greenland, Ph.D. University of Alaska Fairbanks 2013; advisor M. Truffer; publications including Habermann, Truffer, and Maxwell (2013); personal webpage
Numerical simulation of the Antarctic ice sheet and its dynamic response to external perturbation, Ph.D. Potsdam University 2012; advisor A. Levermann; publications including Martin et al. (2011); personal webpage
Modelling the dynamics and boundary processes of Svalbard glaciers, Ph.D. Universiteit Utrecht 2014; advisor J. Oerlemans; publications including van Pelt and Oerlemans (2012) and van Pelt et al. (2013); personal webpage
Large-scale modeling of the Greenland Ice Sheet on long timescales, Ph.D. University Copenhagen 2012; advisors C. Hvidberg and G. Adalgeirsdottir; publications including Solgaard et al. (2011), Solgaard and Langen (2012), and Solgaard et al. (2013); personal webpage
The future sea-level contribution from Antarctica: Projections of solid ice discharge, Ph.D. Potsdam University 2012; advisors S. Rahmstorf and A. Levermann; publications including Winkelmann et al. (2011), Winkelmann et al. (2012), Winkelmann and Levermann (2013); personal webpage
Glacial climate variability, Ph.D. Universität Hamburg 2013; advisor U. Mikolajewicz; personal webpage
We have been notified that two PISM-supporting NASA research proposals have been selected for funding, one in the Cryospheric Sciences program and one in the Modeling, Analysis, and Prediction (MAP) program. Our proposed research threads focus on the dynamics of the Greenland ice sheet and on the exploitation of NASA remote observations as constraints. The current MAP grant expires in the next few months, so this news is timely. The new grants support PISM development and application for four years, through mid-2017. They include support for UAF researchers Ed Bueler, Andy Aschwanden, and Mark Fahnestock, and full-time support for scientific programmer Constantine Khroulev.
In 2012 ten papers were published by scientists using PISM. The articles appeared in these journals:
For details see the PISM Publications tab.
At the AGU Fall Meeting 2012, PISM was prominently featured in several oral presentations.
Speakers presenting PISM results in the video-taped session “C43F: Cryospheric Contributions to Sea Level Rise: Current Estimates and Projections” include
Watch the session online:
See the stable version page to check out a copy of the PISM
stable0.5 source code. If you have already checked out the prerelease version, just do
“git pull” and then
“make install” in your build directory. Send email to firstname.lastname@example.org for help with any version of PISM. See also slides introducing stable0.5 at the European PISM workshop, Hamburg, Germany, May 2012.
Changes compared to
The upcoming stable 0.5 release supports parallel NetCDF4, thus avoiding the file size limitations of netCDF3. This allows for unprecedented grid resolutions.
Here at UAF we have performed the first Greenland 1km 100-year simulations, run in parallel on 512 cores.
Observed and modeled surface speeds in meters per year.
a) observed (Joughin et al., 2010)
b) PISM constant-climate initialization
c) PISM paleo-climate initialization
(click on the image for a bigger version)
The European PISM (Parallel Ice Sheet Model) workshop will be held in Hamburg, Germany, from Monday, the May 21, 2012 (starting at noon), to Tuesday, May 22. Workshop information and registration is available at
Also see this poster.
As of 19 October 2011 we have committed 2000 revisions to PISM in the last five years, for an average of about one commit message per day. We can thank the generous public hosting of PISM at gna.org for this, and subversion too.
By the way, we are at least nine committers: Brown, Bueler, Khroulev, Shemonski, Aschwanden, Martin, Albrecht, Maxwell, Mengel. And quite a few other bug reporters and active users, too! Thanks to all.
But despite wallowing in nostalgia we are going to move source code hosts anyway!
The new host for PISM will be at github, and we will switch to using the git distributed version control system for managing PISM development. This is following the herd! However, with gna's unsigned certificate issues, and not quite keeping up to date, the UAF developers figure it is about time. We expect git will make improving the code easier after a bit of relearning version control. We will officially switch over pism-dev around November 1, but we will continue to host stable versions 0.1, 0.2, 0.3, 0.4 through gna.org. If you are a PISM project member at gna.org you will get an invitation to be a collaborator at the new github site. (Or you can request to be a collaborator at the PISM github site.) Until that invitation announcing the move, please continue to use the gna.org host for commits, bugs, and tasks.
stable0.4 is available. See the stable version page to check out a copy of the source code or download an Ubuntu package. Send email to email@example.com for help with any version of PISM.
Changes (compared to
If you are following the development branch you know that much of the capability developed by Anders Levermann's group at the Potsdam Institute for Climate Impact Research (PIK) is now in PISM. The former PISM-PIK branch of PISM stable0.2 has merged with PISM. This major merge means that PISM is now a joint UAF-PIK project. Both groups are committed to supporting the new capabilities as an open, documented model.
This means all PISM users get a much improved marine ice sheet model, with better ice shelf calving front physics especially.
Our target for release of stable0.4 is May 2011. It will contain the PISM-PIK improvements identified in Albrechts et al. (2011), Martin et al. (2010), and Winkelmann et al. (2010).
If you missed San Francisco in person then you can see some of the talks and posters given by PISM group members. Here's what happened:
See the the UAF ice sheet modeling page for all PISM-related presentations and posters.
stable0.2, the new version